A head up display emits light that reflects from the front windshield to be seen by the driver. The light appears to come from a virtual image in front of the driver and in front of the windshield.
Conventional head up displays create the virtual image by first using a display to create an image. Next, the light from the image is reflected from one or more mirrors, and then the light from the mirrors is reflected from the interior surface of the windshield. The mirrors are designed and positioned relative to the display so that the light seen by the driver, which is reflected from the windshield, appears to come from a virtual image that is outside of the vehicle. The mirrors and display are typically contained in a package that occupies a volume beneath the top surface of the dashboard.
FIG. 1 illustrates an example view from the driver's seat and through the windshield of a vehicle of the prior art with snow on the ground. The lane markers are covered by the snow and are not visible. Thus, the driver may have difficulty judging in which direction to safely steer the vehicle. More particularly, without being able to see the lane markers, the driver may have difficulty keeping the vehicle in its lane.